E! News can exclusively confirm the singer gave birth to a baby girl, her first child with husband Evan Ross, Thursday night. "Their whole family was around to support them," a source reveals. "Evan was very emotional and loves Ashlee so much. He did not leave her side and wanted to go through this with her every step of the way. He can't wait to be a dad. He would do anything for Ashlee and now this baby girl. Ashlee is doing great and can't wait to get home to to be with her family."

Their little arrival joins Ashlee's 6-year-old son Bronx (from her previous marriage to Pete Wentz), who was more than thrilled to become a big brother this summer.

"He's excited. He's so excited," she revealed to E! News after the pregnancy news was announced. "He's excited that it's a girl. He thinks it's cute—the tea parties—she'll be adorable."

Meanwhile, Ashlee was keeping busy throughout her pregnancy by working out at her favorite gym. In fact, E! News learned that the 30-year-old was a big fan of Cardio Barre, a fitness class she attends two to three times a week.

He added, "The dance inspired ballet techniques are no impact/high energy so they are safe to do while pregnant."

Fitness aside, the expectant mother was able to savor her pregnancy that included a "beautiful" baby shower with family and close friends. Back in June, the couple enjoyed a celebration that featured Jessica Simpson and Eric Johnson in attendance.

"The guys got a cabana and hung out for a few hours during the afternoon," a source revealed to E! News. "They ordered food and got some sun."

Meanwhile, Ashlee and her gal pals enjoyed a relaxing and Pinterest-approved day indoors with food and great company. "Ashlee got lots of presents and she had fun opening them with everyone," the insider added of the "beautiful" and "relaxed" evening.

For now, both Ashlee and Evan are excited to have a baby they can call their own. And if someone had their way, more could be in the future.

"I would like [having kids]," Evan told E! News before he learned his wife was expecting. "As many as possible."